Sulfurized grease compositions



Patented Jan. 19, 1954 Joseph A. Dixon,

Berkeley, Calif., assignor to California Research Corporation, San Francisco, Calif., a corporation of Delaware No Drawing. Application March 5, 1952,

' Serial No. 275,027

16 Claims. (Cl. 252-433) This invention pertains to grease compositions containing sulfurized metal soap grease thickening agents (ejg, sulfurized sodium oleate).

Industrial engineers are constantly striving to improve upon engineeringperformance and to incorporate new materials, new techniques, etc. into the various industries. For example, in the automotive industry, there is the desire to manufacture smaller internal combustion engines without sacrificing power output. In fact, many of these smaller engines are designed to deliver greater power than their larger counterparts. The same smaller engines have considerably less bearing surfaces than their larger predecessors, which means that the bearings bear greater loads than before.

Similarly, the continuing trend to manufacture automobiles with lower centers of gravity has made it necessaryto use smaller and smaller gears, particularly in such gear assemblies as the differentials and transmis'sionsQ The smaller ears thus used also have considerably greater pressures exerted upon them per unit area than the older type large gear assemblies. The higher loads on bearings and gears demand better compounding agents in grease compositions.

For quite some period of time, sulfur has been used in lubricating oil compositions for such purposes as, for example, to impart extreme pressure (EQPJ characteristics, anti-wear characteristics,

oxidation'inhibiting' characteristics, etc., to the lubricant. This sulfur has been" obtained from free sulfur, thioethers, mercaptans, mercaptides, etc. However, sulfur compoundswhich are presently used in lubricants for such purposes are known to be corrosive and'to promote wear, particularly to steel and copper surfaces. Thus, it has been necessary to add secondary additives for the specific purpose of inhibiting this corrosiveness caused by the sulfur compounds.

It is, therefore, an object of this invention to prepare grease compositions containing sulfur compounds as extreme pressure agents, which sulfur compounds are not corrosive to steel.

It is a furthe object of this inv ntion to prepare grease compositions having extreme pres-. sure characteristics, anti-wear characteristics, etc, without the use of secondary additives to inhibit corrosion to metals, such as steel and copper, or to inhibit bleeding.

These and further objects of this invention will be apparent from the following description and the appended claims.

According to this invention, it has been discovered that. unexpectedly,

g ease mmpcsinons thickened by metal soaps sulfurized to a critical degree have greatly enhanced anti-wear characteristics while simultaneously being relatively non-corrosive. The grease compositions of this invention comprise lubricating oils and sulfurized metal soaps.

The use of the term sulfurizing herein means the reaction of sulfur with the metal soap thickening agent as described hereinbelow.

In the grease compositions of this invention, metal soaps whichthicken lubricating oils to the consistency of greases are sulfurized. These sulfurized metal soaps are metal soaps of fatty acids having from 1 to 3 double bonds per fatty acid anion. It is preferred that the fatty acid anions contain only 1 double bond. When using fatty acid anions containing 2 or 3 double bonds, it is beneficial to use, addition, small amounts of fatty acids containing only 1 double bond or no double bonds.

The unsaturated fatty acids which are used in the formation of the soaps include the straight or branched-chain, unsaturated fatty acids containing from 9 to 30 carbon atoms.

Examples of unsaturated fatty acids which can be used in the formation of the sulfurized metal soap grease thickening agents according to this invention include undecylenic acid, my-v ristolenic acid, palmitolenic acid, oleic, erucic acid, brassidic acid, cetoleic acid, linolenic acid, linolinic acid, etc.

The metals which can be used in the formation of the soaps include the metals of groups I, II and III of Mendeleefs periodic table. Particular metals include lithium, sodium, potassium, magnesium, calicum, zinc, strontium, cadmium, barium and aluminum.

Although sulfurization seems to be limited to the soaps of unsaturated fatty acids, it is not intended that the grease composition should contain only the soaps of unsaturated fatty acids. Soaps of mixtures of saturated and unsaturated fatty acids may be used in the grease compositions of this invention. However, the soaps of saturated fatty acids do not appear 'to enter into the sulfurization reaction.

The sulfur is present in an amount of from about 0.25 to 1.0 atom of sulfur per double bond.

.' or the unsaturated fatty acid. In other words,

in the average, the unsaturated soap molecule contains from about 0.25 to 1.'0 atom of sulfur for each double bond present, or evaluated as such by the iodine number of the unsaturated soaps. The. value of one atom of sulfur per double bond iscritical; because when its value ex ceeds one, the resulting grease composition has a tendency to bleed, and, also, the grease deteriorates rapidly. I

Suitable base oils include a wide variety of lubricating oilsv such as naphthenic base, paraffin base, and mixed base mineral oils, other hydrocarbon lubricants, e. g., lubricating oils derived from coal products, and synthetic oils, e. g... alkylene polymers (such as polymers of propylene, butylene, etc., and mixtures thereof), alkyiene oxide type polymers, dicarboxylic acid esters, liquid esters of acids of phosphorus and silicon, alkyl benzene polymers, polysiloxanes, etc. Syn thetic oils of the alkylene oxide type polymers which may be used include those exemplified by the alkylene oxide polymers (e. g., propylene oxide polymers) and derivatives, including alley!- ene oxide polymers prepared by polymerizing alkylene oxides, e. g., propylene oxide, in the presence of water or alcohols, e. g., ethyl alcohol, and esters of alkylene oxide type polymer-ac. g., acetylated propylene oxide polymer-s prepared by acetylating propylene oxide polymers containing hydroxyl groups.

Synthetic oils of the dicarboxylic acid ester type include those which are prepared by esteri- *1.

fying such dicarboxylic acids as adipic acid, azaleic acid, suberic acid, sebacic acid, alkenyl succinic acid, fumaric acid, maleic acid, etc., with alcohols such as butyl alcohol, hexyl alcohol 2-ethylhexyl alcohol, dodecyl alcohol, etc. Examples of dicarboxylic acid ester synthetic oils include dibutyl adipate, dihexyl adipate, di- 2-ethylhexyl sebacate, di-n-hexyl fumaric polymers, etc.

Synthetic oils of the alkyl benzene type include those which are prepared by alkylating benzene (e. g., dodecyl benzene, tetradecyl benzene, etc).

Synthetic oils of the type of liquid esters of acids of phosphorus include the esters of phosphoric acid, e. g., tricresyl phosphate; the esters of phosphonic acid, e. g. diethyl ester of decane phosphonic acid, etc.

Synthetic oils of the type of the liquid esters of silicon and polysiloxanes include those exemplified by tetra (Z-ethylhexyl) silicate, hexa (4-methyl-2-pentoxy) disiloxane, tetra (4- methy1-2-pentyl) silicate, tetra (1,3-dimethylbutyl silicate, po1ymethy1 phenyl siloxane, polymethyl siloxane, etc,

Although, as stated hereinabove, the amount of sulfur present in the metal soap thickening agents can be from about 0.25 to about 1.0 atom ofsulfur per double bond of the unsaturated fatty acid anion, the preferred amount of sulfur present in the metal soap thickening agent of grease compositions can vary with the metal of the soap. For example, in a grease composition thickened with calcium soaps, it is preferred to use sulfur in an amount of 0.3 to 0.5 atom of sulfur per double bond in the unsaturated fatty acid anion of the soap; and for a grease com-.- position thickened by lithium, sodium or potassium soaps, for example, it is preferred to use from 0.7 to 0.95 atom of sulfur per double bond of the fatty acid anion of the soap.

It is understood that the amount of soap used the grease compositions of this i vention is that amount which will thicken the. base oil to. the consistency of a grease. Although amounts of about 3% by Weight to about by weight can be used, it is preferred Methods of p epa ing grease composit ons of this invent on includethe following;

to use from about 1. Forming a metal soap from an unsaturated fatty acid, or a mixture of fatty acids containing unsaturated fatty acids, then heating the soap (i. e., the soap itself or a solution or dispersion of the soap in oil) thus formed with sulfur in an amount such that the sulfurized soap contains from 0,25 toLO atom of sulfur per double bond of fatty acid anion, then forming the grease therefrom by adding the proper amount of oil.

2. Reacting sulfur with a grease composition comprising a lubricating oil thickened by a metal soap of an unsaturated fatty acid, etc.

The reaction of the sulfur and the soaps of unsaturated fatty acids can be accomplished at temperatures between 225 F. and 600 F. The period of time required for the reaction depends on the temperature at which the reaction is accomplished and the amount of sulfur which is to be incorporated into the soap. The higher the temperature, the less the reaction time necessary for the completion of the reaction.

The exact nature of the reaction between the sulfur and the soaps of the unsaturated fatty acids is not known. It is not known in what manner the sulfur combines with the metal soaps. The degree of unsaturation of the fatty acid remains practically the same after the reaction with the sulfur as before the reaction; that is, the iodine number of the fatty acid is practically the same after the reaction with the sulfur as before, It is fairly well established that the reaction of sulfur with the metal soap is not accomplished at the expense of the double bond of the fatty acid anion.

As stated hereinabove, the soap thickening agents may also contain soaps of saturated fatty acids. It is preferred that the soaps of unsaturated fatty acids are present in amounts of more than 15% of the total amount of fatty acids. However, when the amount of sulfur p s about one atom of sulfur per double bond, the total amount of unsaturated fatty acid anion may be only 5% of the total amount of fatty acid anions.

The use of the sulfurized metal soaps in grease compositions according to this invention enhances extreme pressure characteristics, antiwear characteristics, etc., but still the grease compositions of this invention are non-corrosive to copper and steel. Furthermore, the grease compositions of this invention have greater sistance to oxidation. reater resistance to bleedin and have a better texture than greases thickened with unsulfurized scans The grease compositions sulfurized according the present invention can be prepared by methods exemplified by the followin EXAMPLE 1.-PREPA-iwr1oiw or A SULFURIZEU LITHIUM SOAP GREASE A mixture of 28.2 grams (0.1 equivalent) of highly refined oleic acid, 28.4 grams (0.1 equivalent) of stearic acid and 391 grams of a California solvent-refined paraffin base petroleum oil having a viscosity of 185 SSU at 210 F., was heated with. stirring to 170 at which tem perature the acids were neutralized by ml. of.2N lithium hydroxide solution. This whole mixture was heated with stirring to 400 F., at Whi h temperature grams ofsulfur was added. After-the -reaction mixture had been heated at a temperature ranging from 410 to 420 F. for two hour h roduct was cooled in a large evaporating dish.-

EXAMPLE 2.-PanPAaA*rionor A SULFUBIZED Sonron lent) of sodium hydroxide was added to a mixture of 14.2 grams (0.05 equivalent) of stearic acid, 14.1 grams (0.05 equivalent) of oleic acid, and 76.5 grams of California solvent-refined paraflin base oil having a viscosity of .480 SSU at 100 F. This mixture was heated with stirring to 430 F., and sufllcient stearic acid wasadded to adjust the pH to 7.0. The solution was cooled in an evaporating dish, resulting in the formation of a pale brown, smooth, soft grease. To this grease was added 1.3 grams of sulfur, and the mixture was heated with stirring to 400 F. for 1 hour. The resulting product was a very soft, smooth grease containing 0.82% sulfur.

-EXAMPLE 3.PREPARATION 0F SULFURIZED SODIUM SOAP GREASE An aqueous solution of 4.0 grams (0.1 equivalent) of sodium hydroxide was added to a mixture of 14.2 grams (0.05 equivalent) of stearic acid, 14.1 grams (0.05 equivalent) of oleic acid. and 76.5 grams of California solvent-refined paraffin base oil having a viscosity of 480 SSU at 100 F. This mixture was heated with stirring to 430 F., and suflicient stearic acid was added to adjust the pH to 7.0. The solution was cooled in an evaporating dish, resulting in the formation of a pale brown, smooth, soft grease. To this grease was added 1.3 grams of sulfur, and the mixture was heated at 250 F. for 24 hours. The resulting product was a soft, smooth grease.

number=52). 610 grams of hydrated lime, 2000 grams of a California solvent-refined paraflin base oil having a viscosity of 450 SSU at 100 F. and 500 m1. of water was heated at 300 F. for one hour in a, grease kettle at an absolute pressure of about pounds per square inch. After the temperature had been reduced to 200 F. and the pressure reduced to atmospheric pressure, sufiicient stearic acid was added so that the mixture had a content of about 0.1% free fatty acid. The whole mixture was heated to 300 F., at which temperature 200 grams of sulfur was added, and the sulfurization reaction was continued at 300 F. for 3 hours. After the mixture had been cooled, 6500 grams of the above petroleum oil was added, and the grease was hydrated by the addition of 425 ml. of water at a temperature of 235 F., which cooled the grease to 215 F. An additional amount of 11,200 grams of a California solvent-refined parafiin base petroleum oil having a viscosity of 140 SSU at 210 F. was added. The resulting grease had a melting point of 212 F., an unworked penetration of 321 and a worked penetration of 355 (60 strokes).

The following Table I presents reaction conditions, inspections and general data. on sulfurized metal soap greases of this invention. Base oil A was a California solvent-refined paraffin base oil having a viscosity of 185 SSU at 210 F.; base oil "3 was a California solvent-refined parafiin base oil having a viscosity of 480 'SSU at 100 F; and base oil "0 was a California solventrefined paraflin base oil having a viscosity of 450 SSU at 100 F.

Teen: I

Reaction conditions and properties of sulfurized metal soap greases I sulfurization reaction Penetration Sulfur Soap ASTM Test (percent Base s 5 3' dropy 011 mole of Temp Time grease I mpg Unworked weight) e (hrs) pomt Worked 60 ated fatty 7 strokes acid anion) 12 C 1 10. 0 A 0- 0 376 234 279 12-CS 1 10. 0 A 0. 5 400 .1 388 305 286 15-25. 1 10. 4 A 0. 5 250 24 0. 71 400+ 261 330 15-35. 1 10. 4 A 0. 5 400 1 0. 51 402 260 307 22A 14.0 A 0.0 382 22B 14. 0 A 0. 9 400 1 O. 389 203 260 22-0 1 14.0 A 0.9 250 24 0.06 393 216 207 23-6 2 26. 8 B O. 9 400 1 0. 82 366 305 331 23-A z 26. 8 B 0. 0 364 290 332 45-A 3 20. 0 C 0. 0 206 183 207 42-A 3 20. 0 C 0. 9 300 2 0. 87 348 370 1 Equal parts by weight 9 Equal parts by weight 5 Calcium soap of a tallow EXAMPLE iv-PREPARATION 'OF A LITHIUM SOAP GREASE EXAMPLE 5.PREPARATION on A CALCIUM SOAP GaaAsE A mixture of anagrams a an... (iodine of lithium oleate and lithium stearate.

iii)

of sodium oleate and sodium stearate.

having an iodine number of 52.

The data presented hereinbelow in Table II show the effectiveness of sulfurized metal soap thickening agents in reducing wear and in increasing the extreme pressure properties of greases, comparisons being made with greases prepared from unsulfurized metal soap thickening agents. The soap used, was a calcium soap of a tallow having an iodine number of 52. The sulfurization reaction wasaccomplished at300 F. for a period of 2 hours.. The Timken and Almen tests are described in Lubricantsand Lubrication" by 'Clower, published by McGraw-Hill Book Company in 1939, pagesto 148, inclusive; The Falex tests aredescribed in the Jourr nal of the Institute of Petroleum, vol. 32, April 1946. In the following table, base o il .'.D was a mixture of California solvent-refined para'fiin asset-a4 1 base oil having a viscosity of: 185 SS at 210 F; and a" California solvent-refined. base. oil having a viscosity of 450 SSU at 100 F. Base oil C was the same as described. in connection with Table I.

TABLE II" 7 Reaction conditions and wear characteristics of sulfurzzed. metal soap greases Y Sulfur-F Faleictests cation I g-i -Almen. Timkcn z "11mm test test Soap (gm, 7 EXL Test (per 'Base atoms] Wear Exems tmmev No. 'ccntby oil molizo'iE (I25 trcmc pres weight). unsatulbs.) pres- Sure. sure rated (mgmsg sure (lbs) abs fatty" loss) (lbs) acids anion) I-A. 12.0 1 D 1.0 1,550 15 15 18-0 c 18.0 D 0:9 (LT 3,100. 1843 18.0 D 0.9. 1.1 3,000 l- 30 42'-A 20.0 O 010 38 42-3, 20.0 O 0.43 M... f 38 In addition to the soap thickening agent, grease samples Nos. 1-A.. and 18-0 contain 9%, by weight, white lead. The tests of Table II show that greases thickened with sulfurized metal soap thickening. agents have double the extreme pressure values compared. with greases thickened with unsulfurized. metal soap thickening agents. Furthermore, the presence of white lead does not appear to enhance these characteristics of greases thickened with sulfurized metal soaps.

The corrosivity of greases thickened with soaps prepared by sulfurizing unsaturated free fatty acids first, then saponifying the sulfurized fatty acid to for-m the metal soap grease thickening agent was compared with greases thickened with sulfurized metal soaps prepared by sulfurizing the metal soaps directly.

The corrosivity of these greases was determined" by immersing a polished copper strip in a 50 ml. beaker filled with the test grease at 190 F. for 100 hours. The copper strip was then washed with hexane and dried. A copper strip which was still bright after the test received a copper V strip test evaluation of-10. A strip which was beginning to show a slight indication of tarnish, received an evaluation of '7. A black strip was evaluated at 3, and a strip which was black and peeling, an evaluation of 0.

Grease 7-D was prepared by first sulfurizing a mixture of fatty acids consisting of byv weight, of oleic acid and 50% stearic acid by' reacting 0.9 gram atom of sulfur per mole of oleic acid at 400 F. for 1 hour, then forming a lithium soap. The final grease composition contained 15.5%, by weight, of the soap thus formed plus 84.5% of a California solvent-refined paraffin base oil having a viscosity of 480 SSU at 100? F; This grease had a copper strip corrosion number of 3.

Grease 7-E was prepared by forming a lithium soap from a mixture of fatty acids consisting of 50%, by weight, of oleic acid and 50% stearic acid, then reacting the lithium soap with 0.9 gram atom ofsulfur per mole of oleic acid at 400?" F. for 1 hour. The finalgrease composition-contained 15.5%, by weight,of the sulfurized lithium soap thus formed and 84.5% of a California solvent-refinecl parafiiln base oil'having a viscosity of 480 SSU at 100 F. This grease had a copper strip corrosion number of 7. The copper strip was only slightly tarnished, not corroded. I The greases of the presentinvention may also contain. other agents whichwill enhance, for example, oxidation inhibition, corrosion inhibition, etc. Other agents such as. polybutenes. may be added as stri'nginess agents, and still other agents may be added as fillers, dyes, etc- The sulfurized metal soap thickening agents of this invention can also be used in conjunction with other thickening agents. in grease compositions to inhibit wear. For example, it. is known that considerable wear with steel on steel surfaces is prevalent when polysiloxane grease compositions are used as lubricants- However, when sulfurized metal soaps (e. g.,. sulfurized sodium oleate) are incorporated into. silica. thickened polysiloxane (e. g., a. polymethyl phenyl siloxane) grease composition, the. wear is considerably reduced.

I claim:

I. *A grease composition comprising a major proportion of an oil of lubricating viscosity and from 3% to 50% of a sulfurized metal. soap thicke'ning agent obtained by reacting. sulfur with a metal soap of an unsaturated fatty acid and congaining from 0.25 to 1.0 atom of sulfur per double ond.

2.v A. grease composition comprising a major proportion of an oil of lubricating viscosity and .a sulfurized. metal soap thickening agent obtained by the reaction of sulfur with a, soap of an un saturated fatty acid and containing from 0.25 to 1.0 atom of sulfur per double bond said thick ening' agent being present in an amount sufficient to thicken the oil to the consistency of a grease. v 3. A grease composition comprising a major proportion of an oil of lubricating viscosity and from 10% to 25% of a sulfurized metal soap grease thickening agent obtained by reacting sulfur with metal soaps of unsaturated fatty acids and containing from 0.25 to 1.0 atom of sulfur per double bond.

4. A grease composition comprising a, major proportion of an oil of lubricating viscosity and from 3% to 50% of a metal soap grease thickening agent, at least 5% of said soap grease thickening agent being a sulfurized metal soap thickening agent obtained by the reaction of elemental I sulfurwith metal soaps of unsaturated fatty acids and containing from 0.25 to 1.0 atom of sulfur per double bond.

5. A grease composition comprising a major proportion of an oil of lubricating viscosity and from 3% to 50% of a metal soap grease thickening agent, at least 15% of said soap grease thickening agent being a sulfurized metal soap thickening agent obtained by the reaction of elemental sulfur with metal soaps of unsaturated fatty acids and containing from 0.25 to 1.0 atom of sulfur per double bond.

6. A grease composition comprising a major proportion of an oil of lubricating viscosity and from 3% to 50% of a metal soap grease thickening agent, at least 5% of said metal soap grease thickening agent being a sulfurized alkali metal soap grease: thickening agent obtained by the reaction of sulfur with alkali metal soaps of unsaturated fatty acids and containing from 0.25 to 1.0 atom of sulfur per double bond.

:7. The grease composition of claim 6, wherein the alkali metal soap is a sodium soap.

8. A grease composition comprising a major proportion of an oil of lubricating viscosity and from 3% to 50% of a metal soap grease thickening agent, at least 5% of said metal soap grease thickening agent being a sulfurized polyvalent metal soap grease thickening agent obtained by the reaction of sulfur with polyvalent metal soaps of unsaturated fatty acids and containing from 0.25 to 1.0 atom of sulfur per double bond.

9. A grease composition comprising a major proportion of an oil of lubricating viscosity and a metal soap grease thickening agent in an amount suflicient to thicken said 'oil to the consistency of a grease, said metal soap grease thickening agent containing at least 5% sulfurized metal soaps obtained by reacting elemental sulfur with metal soaps of unsaturated fatty acids having from 9 to 30 carbon atoms and from 1 to 3 double bonds per fatty acid anion, said sulfurized metal soap containing from 0.25' to 1.0 atom of sulfur per double bond.

10. A grease composition comprising a major proportion of an oil of lubricating viscosity and a metal soap grease thickening agent in an amount sufficient to thicken said oil to the consistency of a grease, said metal soap grease thickening agent containing at least 15% sulfurized metal soap obtained by reacting elementalsulfur with metal soaps of unsaturated fatty acids having 9 to 30 carbon atoms and from 1 to 3 double bonds per fatty acid anion, said sulfurized metal soap containing from 0.25 to 1.0 atom of sulfur per double bond.

11. The grease composition of claim 9, wherein the sulfurized metal soap is a sulfurized alkali metal soap of an unsaturated fatty acid.

12. The grease composition of claim 9, wherein the sulfurized metal soap is a sulfurized sodium soap of an unsaturated fatty acid.

13. The grease composition of claim 9, wherein the sulfurized metal soap is a sulfurized polyvalent metal soap.

14. The grease composition of claim 9, wherein the sulfurized metal soap is a sulfurized calcium soap.

15. The grease composition of claim 9, wherein the sulfurized metal soap is sulfurized sodium oleate.

16. The grease composition of. claim 9, wherein the sulfurized metal soap is sulfurized calcium oleate.

JOSEPH A. DIXON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,957,259 Gallsworthy May 1, 1934 2,212,189 Brunstrum Aug. 20, 1940 

1. A GREASE COMPOSITION COMPRISING A MAJOR PROPORTION OF AN OIL OF LUBRICATING VISCOSITY AND FROM 3% TO 50% OF A SULFURIZED METAL SOAP THICKENING AGENT OBTAINED BY REACTING SULFUR WITH A METAL SOAP OF AN UNSATURATED FATTY ACID AND CONTAINING FROM 0.25 TO 1.0 ATOM OF SULFUR PER DOUBLE BOND. 